Kenneth Clarke was under growing pressure last night to investigate fresh evidence that British American Tobacco exploited cigarette smuggling.

The former chancellor and health secretary, now the London-based multinational's deputy chairman, has a legal duty to protect the company's integrity.

BAT documents reveal that huge numbers of cigarettes produced in Southampton, one of the most modern tobacco plants in the world, and other factories were made for the Far East, Middle East and Asia - markets which are dominated by black marketeers.

Mr Clarke, paid nearly £68,000 for the part-time post, yesterday failed to respond to repeated requests for a comment about the serious allegations.

Mr Prideaux, a member of the company's management board, said it would reply at an unspecified time in the future.

Today's revelations about the exploitation of smuggling in the Far East, Middle East and Asia follow Monday's disclosure in the Guardian of how the company benefited from black marketeering in Latin America.

BAT stonewalled as Labour MPs demanded explanations from the world's second largest tobacco company.

Kevin Barron, the chairman of the all-party group on smoking and health, said: "Ken Clarke holds his position within BAT because of his past office as chancellor and health secretary.

"He has a wider public duty to answer what are very serious allegations about smuggling."

Fraser Kemp, Labour MP for Houghton & Washington East, said: "The company cannot bury its head in the sand and hope all this will go away.

"Very serious allegations have been made and Kenneth Clarke and his fellow directors have a responsibility to answer them now."

The all-party Commons health committee is considering whether to recall BAT's non-smoking chairman, Martin Broughton, or ask for fresh evidence as part of its inquiry into the tobacco industry.

On Monday night, a senior World Health Organisation official promised a clampdown on powerful tobacco companies with an international treaty planned to curb their activities.

BAT sells 900bn cigarettes a year and is challenging US-based Philip Morris for pole position in the global tobacco business.